Future generations of cellular networks are expected to provide high data rates, up to several Gbps while at the same time being energy efficient. One possible way to achieve such high data rates and/or to lower the energy consumption in cellular networks is to deploy reconfigurable antennas systems (RAS). RAS is an antenna system whose radiation characteristics can be changed by the network after deployment and adapted to, e.g., current traffic needs. The most common antenna parameter that can be remotely controlled has been the antenna tilt. Technology advances will introduce more possibilities to modify the antenna lobe shapes, far beyond the one-dimensional tilt, which opens up for new possibilities to improve network performance. For example, the antenna system can be reconfigured to better serve a traffic hotspot by, e.g., increasing the antenna gains toward the hotspot location.
To efficiently use RAS, it has to be automatically controlled, for example by using a self-organizing network (SON) algorithm which is called RAS-SON. It is important to distinguish RAS from UE-specific beamforming. RAS is used to shape the cell-specific beam patterns for cell-specific reference signals (CRSs) and control signals, and is typically changed quite slowly, accommodating for changes in the infrastructure or user behaviors, for example on an weekly basis. The UE-specific beamforming is used to shape the beams for UE-specific signals and is typically changed very quickly, for example on a millisecond basis.
Tuning RAS settings for base stations in a wireless network by using SON-algorithms can take several weeks for a large area, for example since there exists many different combinations of possible RAS settings in a network and each RAS setting is typically evaluated during quite long time (hours or days) in order to gather enough statistics. Operators have a resistance against changing antenna parameters in their network after deployment due to the risk of creating coverage holes. One solution to minimize this risk is to change the antenna parameter settings with very small steps, for example the tilt might only be changed and evaluated by one degree at a time. However, when using such small steps, for example antenna beam tilt steps, the time consumption is increased even further.
There is thus a need for controlling a configuration algorithm arranged to optimize the beam pattern, such as RAS-SON, to run more efficiently.